1. Field of the Invention
The present invention relates generally to moldable articles and compositions for making the same. In particular, the invention relates to articles that are heat-moldable.
2. Background Art
It is becoming more and more desirable to provide wearers with customized articles for sporting goods and the like. Such articles provide the wearer with a greater degree of comfort and support. One way this customization can be achieved is by producing articles that simulate the contours of a particular part of the body on which they are worn or used. Examples include footbeds that simulate the bottom contours of the human foot, racquet handles that simulate the contours of the hand, helmets that simulate the contours of the head, and shin pieces that simulate the contours of the lower leg.
A number of approaches have been developed to provide customized articles. In one approach, the article includes a layer of thermoplastic material which will soften when heated. The wearer then presses a body part against the heated article, creating an impression. The thermoplastic material is then allowed to cool while retaining the impression of the wearer""s body part. An example of this approach is disclosed in U.S. Pat. No. 5,733,647. In this example, the thermoplastic material comprises a mixture of ethylene copolymers and/or ethylene terpolymers with an ethylene terpolymer such as ethylene vinyl acetate coploymer modified by the addition of carbonyl groups incorporated as part of the main chain. While the thermoplastic material disclosed in U.S. Pat. No. 5,733,647 can be heated and molded, it is a non-foam material which reduces the comfort provided by the article and microwave heating a thermoplastic material that includes carbonyl groups in the main chain can result in the emission of toxic carbon monoxide fumes. Obviously, this is dangerous for consumers who may choose to mold the article at home.
Thus, the need exists for an article which can be custom molded in a simple and efficient manner, without the possibility of emitting toxic fumes.
The present invention solves the above stated problems by providing an article that is efficiently heat-molded without releasing carbon monoxide and which can be re-heated and re-molded. In particular, the article comprises a layer of modified ethylene vinyl acetate copolymer. Preferred modifying agents include polyol amines such as ethoxylated amines, ethoxylated fatty alcohols, phosphoric acid esters, quaternary ammonium salts, and amphoteric compounds such as betaine. An article made from this composition can be heat-molded quickly and efficiently. The moldable article may be heated using microwave heating or other known heating methods. During heating, the article does not release carbon monoxide. Once heat-softened, an impression is formed in the article using, e.g., a body part, such as a head, foot, or lower leg. After the impression is created in the softened article such that it conforms to the contours of the body part, the article is allowed to cool, resulting in a custom-fitted article. If the user is unhappy with the impression or uncomfortable with the fit, the process can be repeated by re-heating the article and re-creating the impression.